1. Field of the Invention
This invention relates to conservatively transforming carbonaceous matter into fuels and petrochemicals for power and other purposes.
2. Description of the Prior Art
There have been many attempts to improve the efficiency of power generation systems in order to reduce the fuel consumption/power generated ratio, and to reduce environmental pollution from combustion products. Some of those attempts include gas turbine blade cooling, combined cycle heat recovery, and the Humid Air Turbine (HAT) cycle. For example, U.S. Pat. No. 4,829,763 discloses an intercooled, regenerative cycle with a saturator that adds considerable moisture to the compressor discharge air so that the combustor inlet flow contains 20 to 40% water vapor. The water vapor adds to the turbine output while the intercooling reduces the compressor work requirement which result in higher specific power. The compressed air which is used for combustion of the fuel to drive the turbine is cooled then humidified prior to combustion in a multistage counter-current saturator with the aforementioned water vapor. Low level heat is rejected from the compressed air during intercooling and prior to humidification. The HAT cycle is an improvement in thermal efficiency compared to the combined cycle, the steam injected cycle, the intercooled regenerative cycle and other humidification based processes. The HAT cycle requires very high air pressures up to 30 atmospheres and higher turbine inlet temperatures up to 2800 F. to improve overall plant thermal efficiencies.
Another system is considered to be an extension to the HAT cycle, and is called the Integrated Gasification Humid Air Turbine (IGHAT) has been described by Day and Rao as a method of coal gasification based power generation that could provide high efficiency and low emissions at least comparable to an integrated gasification combined cycle (IGCC) but without the penalty of high capital cost that is usually associated with IGCC systems. Much of the cost savings from IGHAT comes from the fact that the HAT cycle can use low level heat from gasification quench water in an efficient way via the saturator, whereas in an IGCC one must recover as much heat as possible from the raw coal gas in the form of high temperature and high pressure steam, using relatively expensive waste heat boilers. Additional cost savings occur because the cycle does not require a steam turbine condenser. Further, the large amount of water vapor mixed with combustion air is expected to reduce NO.sub.X emissions to very low levels, assuming suitable combustion can be achieved at reduced flame temperatures.
Harvey et al., describe a process for reducing combustion irreversibility through off-gas recycling. The process has no bottoming cycle which is similar to a gas turbine with intercooling, reheating and a regenerator. The regenerator functions as a reformer wherein the fuel is cracked and partly oxidized by heat from the recycled turbine off-gases. The off-gases contain oxygen and thus are used as oxygen carriers. Before each turbine stage, air is injected into the gas stream containing reformed fuel and recycled off-gases which are thereby sequentially fired. The water vapor in the off-gases is partially liquefied in the series of water-cooled condensers after each stage; intercooling is accomplished by injection of the water. Analysis by Harvey, et. al. shows reforming for fuel conversion, but the gains presented were limited by pinch point temperature in the reformer. Harvey, et al. plan further study of the effect of their proposed arrangement on efficiency at turbine inlet temperatures below 2300 F., which in the analysis is the approximate high limit without turbine blade cooling.
To control turbine inlet temperature within acceptable metallurgical limits (now 2600-2800 F.) gas turbine designers have resorted to excess combustion air, diluents such as steam as in HAT or simple steam injection, water injection or compressor intercooling. Concurrently metallurgists are working to develop ceramic components or coatings which can tolerate ever higher temperatures. This invention achieves turbine inlet temperature control by turbine exhaust recycle with consequential high system cycle efficiencies. Capital is reduced by rocket engine reactor compactness and elimination of combined cycle equipment and its related efficiency reducing system infrastructure. In dealing with the exhaust from steam turbines, this invention utilizes much of the latent heat in the exhaust with consequent reduction in the cooling water load otherwise required for condensing steam for boiler feed water.
It is therefore an object of the present invention to provide a method of generating power from fuel with improved efficiency over prior methods, employing conventional turbine inlet temperatures without diluent injection or intercooling. Another object is to provide apparatus for generating power from fuel in a more flexible, efficient and less polluting manner than prior art methods, at reduced capital cost.
This invention can also be used as a pyrolysis reaction system to carry out either moderate temperature conventional pyrolysis or high temperature total pyrolysis. U.S. patents by Raniere, et al. U.S. Pat. No. 4,724,272 and Hertzberg, et. al. U.S. Pat. No. 5,300,216 teach that heating and quench in transonic flow must be accomplished at precise residence times with respect to shock type and shock location. Both hydrocarbon and steam are heated and passed through separate supersonic nozzles before pyrolysis. Hertzberg further teaches that, after quenching, the cracked gases may be passed through a turbine for energy recovery and further cooling.
With this invention combined fuel conversion transformations and pyrolysis are also possible. U.S. Pat. Nos. 4,136,015 and 4,134,824 by Kamm, et. al. teach a process for thermal cracking of hydrocarbons and an integrated process for partial oxidation and thermal cracking of crude oil feed stocks. Hydrogen available from heavy oil partial oxidation promotes yield selectivity. Moderate time-temperature cracking conditions are selected which result in substantial liquid product and tar yields which must be handled with difficulty within their process and in downstream processes.
It is therefore an object of this invention to provide a method of pyrolyzing and hydropyrolyzing carbonaceous matter either alone or in combination with fuel conversion transformations at moderate or high temperatures and pressures, achieving near total feed stock conversion, in a near total energy conservation arrangement. Another object of this invention to provide apparatus for pyrolyzing and hydropyrolyzing carbonaceous matter either alone or in combination with fuel conversion transformations at moderate or high temperatures and pressures, achieving near total feed stock conversion, in a near total energy conservation arrangement.